Communication system networks are known to include multiple communication systems linked together through a processing multiplexer. Within each of the multiple communication systems, a signal router is used to control the flow of communication system data signals (i.e., time-division multiplexed (TDM) frames of digital audio information) between operator stations and base stations. The base stations relay the audio and control information-under the control of the signal router--to/from communication units (e.g., mobile/portable radios) within each communication system, typically via radio frequency (RF) channels. In addition to routing audio information within their respective communication systems, the signal routers support interconnection with the processing multiplexer, allowing audio information sourced by each signal router to be shared with other signal routers, and in this manner lead to the establishment of communication system networks.
Often, a signal router within a given communication system supports multiple operator stations. Furthermore, each operator station can typically monitor multiple talkgroups (i.e., a group of logically related communication units configured to transceive communications relating to the entire group). To support these requirements in a communication system network, switching centers within the processing multiplexer (each uniquely associated with one of the communication systems) sum communication system data signals associated with the relevant talkgroups. That is, simultaneously occurring data frames within the communication system data signals are added together by dedicated switching centers. The resulting summed communication system data signal is then routed to the appropriate operator station via the required signal router. For a more complete discussion of the operation of the processing multiplexer and the switching centers, reference is made to U.S. Pat. No. 5,175,727 entitled COMMUNICATION SYSTEM NETWORK INTERCONNECTING A PLURALITY OF COMMUNICATION SYSTEMS, assigned to Motorola, Inc., and incorporated herein by reference. The number of summing operations any switching center can perform within the period of a single data frame is limited by the processing capability of presently available technology.
To illustrate this limit, it is assumed that the switching centers are Ambassador boards and that the processing multiplexer is an Ambassador Electronics Bank, both manufactured by Motorola, Inc. Also assuming that the period of each data frame is 125 .mu.s., the switching centers, as described, are currently limited to performing no more than 1746 summing operations per data frame. Thus, if a given signal router supports 30 operator stations, and each operator station monitors 50 talkgroups, then a total of 3000 summing operations (2.times.30.times.50) need to be performed. The factor of two shown above occurs because each talkgroup requires two summing operations per data frame (in this way both parties talking can be monitored; one for the talkgroup and one for the operator station). Since 3000 summing operations per data frame cannot be supported by a single switching center, the communication system must be divided using multiple signal routers each having fewer associated operator stations. Of course, this solution is undesirable, as the additional signal routers and communication links (typically T1/E1 type phone lines required to establish connections to the processing multiplexer) required results in a system that is cost prohibitive.
Another potential solution is to upgrade the processing capability of the switching centers as more powerful processing technology--e.g., faster microprocessors--becomes available. This solution is also undesirable due to the significant costs that would occur as a result of the redesign and purchase of upgraded switching centers.
Therefore, a need exists for a method that increases the summing capability of a switching center, and thereby augments listening capacity of a signal destination having excessive summing requirements. Such a method would not require the division of existing communication systems to more evenly distribute the excessive requirements.